Thread: Theory questions about Java

Originally Posted by susan12

1) If a class is not abstract but it has an abstract method, is it true that it still CAN NOT be instantiated? Or do abstract methods only exist inside abstract classes?

The animal doesn't exist. If it has abstract methods, it must be an abstract class or interface.

2) The purpose of an abstract METHOD is to make sure the subclass overrides the method but what's the purpose of an abstract CLASS? Is the purpose of an abstract CLASS to be able to store the abstract METHODS? (that is IF I am right in saying that abstract methods HAVE TO BE in abstract classes)

Having the class be abstract forces you to extend the class, to create a concrete subclass before using it.

3) Imagine I had an array called, and set up as, array[rows][columns]. Doing array.length would give me the length of the rows but is array[].length the way to get the length of the columns?

No, you have to give the row number, i.e., array[0], because you can have ragged arrays with different length of each row.

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Any input would be greatly appreciated!
Thanks in advance![/QUOTE]